DSL is going to be as reliable as your local carrier. Its gonna be no better, no worse than Cable depending on the area. If cable is not working for you, then DSL can't be any worse.

I am using Comcast right now. Its been nearly 100% reliable for me. A colleague of mine in an area about an hour north uses Comcast -- he's got the exact opposite position.

One thing to mention about DSL. Your experiences with DSL will be reliant on your distance from the Central Office. FIOS is different -- and if you can get that, it might be the best alternative.

Another thing, if you are planning to go DSL, do some homework. You don't necessarily have to get it from your local carrier. It will go through your carrier but you might be better (pricewise) to get it from a company like Covad or DSL Extreme.